Fluorinated acyl peroxides



Patented July 10, 1951 FLUORINATED ACYL PEROXIDES Orville H. Bullitt, Jr., Swarthmore, Pa., assignor to E. I. du Pont de Nemours and Company, Wllmington, Del., a corporation of Delaware No Drawing. Application March 4, 1950, Serial No. 147,756

8 Claims. (Cl. 260-610) This invention relates to a new class of fluorinated organic compounds. More particularly, it relates to new fiuorinated acyl peroxides and to a method for their preparation.

Because of superior qualities of the recently introduced cold" synthetic rubbers, low temperature polymerization has taken on increased importance in the field of plastics. In spite of this singular success, however, there is still a great need for polymerization catalysts capable of initiating satisfactory polymerization at low temperatures of not just a few, but a wide variety of ethylenically unsaturated monomers.

An object of the present invention is to provide a new class of fluorinated organic compounds and a process of preparing same. A further object is to provide new fiuorinated acyl peroxides capable of initiating satisfactory polymerization at low temperature of a wide variety of ethylenically unsaturated monomers. Other objects will be apparent from the description of the invention given hereinafter.

The above objects are accomplished according to the present invention by the provision of a new class of fluorinated organic compounds, namely, the fiuorinated acyl peroxides having the formula,

wherein B is hydrogen or fluorine and n is an integer of at least two. The preferred peroxides are those in which n is an integer from 2 to 24, inclusive, and still more preferably, from 2 to 12, inclusive.

It will thus be seen from the above that the fluorinated acyl peroxides of this invention are the di(polyfluoroalkanoyl) peroxides having, exclusive of the group,

at least two fluorine atoms on every carbon atom, any other atom being hydrogen on each of the two terminal carbon atoms. Otherwise stated, these compounds are the di(polyfiuoroalkanoyl) peroxides of the straight chain polyfluoroalkanoic acids which, exclusive of the carboxyl carbon atom, have at least 2 and, preferably, not more than 24 carbon atoms, all of which bear at least 2 fluorine atoms, the terminal or omega-carbon atom bearing also a hydrogen or a third fluorine atom, and the more preferred compounds are the peroxides of these straight chain polyfluoroalkanoic acids which, exclusive 2 of the carboxyl carbon atom, have at least 2 and not more than 12 carbon atoms.

A convenient method for preparing the new peroxides of this invention comprises reacting a polyfluoroalkanoyl halide of the formula,

wherein B and n are as defined above and X is chlorine or bromine, with an inorganic peroxide such as an alkali or alkaline earth metal peroxide, e. g., sodium, calcium, and barium peroxide, at a relatively low temperature such as 40 C. to +5 C., preferably, between 20 C. and 5 C. While the reaction mixture may be allowed to rise to higher temperatures up to +25 0., as a precautionary measure temperatures not in excess of +5? C. are advisable.

In a preferred mode of preparing these peroxides, a polyfluoroalkanoyl chloride,

B (CF2) nCO'Cl is added gradually, as dropwise, at a temperature of 20 C. to 5 C. to an aqueous solution of sodium peroxide in the amount of at least one mole of sodium peroxide for each two moles of the polyfluoroalkanoyl halide added and the reaction is continued to completion, usually a period of 10 to 20 minutes and not more than one hour after mixture of the reactants. The resulting di(polyfiuoroalkanoyl) peroxide may then be isolated by extraction and crystallization. Although not essential, it is usually desirable to use an excess of the inorganic peroxide, for example, 5% to 15% molal excess, over the molal amount of polyfluoroalkanoyl halide employed since an excess of inorganic peroxide in the reaction mixture after completion of the reaction may be readily removed whereas excess of the polyfluoroalkanoyl halide is not so readily removed and, in addition, may create further complications.

Other reaction media besides water, for example, Water-soluble alcohols such as methanol. ethanol, and mixtures of water with these alcohols, can be employed for dissolving the inorganic peroxide. Best results are in general obtained with water alone. The amount of reaction medium employed can vary widely. Twenty to parts of water per part of sodium peroxide, for example, usually gives satisfactory results and constitutes the preferred proportion.

The resulting di(polyfiuoroalkanoyl) peroxide is conveniently isolated from the reaction mixture by extraction and/or crystallization. Suitable solvents for this purpose include perfluorooi! polyfluoroalkanoic acids, F(CF2)1|COOH, which methylcyclohexane, petroleum ether, butane, have recently been described by Reid and Smith heptane, diethyl ether, methylene chloride. and (Abstracts of Papers, page 9K, 116th Meeting, the like. Alter extraction at -20 to C. with American Chemical Society, September 1949), one of the above solvents, .the peroxide can usumay be made by this method. ally be crystallized on cooling the extract to a The invention is illustrated in greater detail in suiliciently low temperature, 75 C. to 25 th following examples in which parts, unless C., at which point the solid peroxide may be reotherwise specified, are by weight: moved from the solvent by filtration. Exam 16 I The polyfluoroalkanoyl chlorides and bromides, m p employed as starting materials in the synthesis To 20 parts of water cooled to 0 C. was added of the peroxides of this invention, can be prewith stirring 0.42 part of sodium peroxide. This pared from the corresponding polyfluoroalkanoic solution was cooled to 5 C. and 5 parts oi! acids by treatment, for example, by refluxing, sodium chloride was added. When the temperawith a halogenating agent such as thionyl chloture had reached l5 C., 2.7 parts of octafluororide, thionyl bromide, phosphorus trichloride, pentanoyl chloride, H(CF2CF2)2COC1, was slowly phosphorus tribromide, phosphorus oxychloride, added dropwise. The temperature rose to -ll etc., preferably in the presence of an acid ac- C. with the cooling bath at C. and then ceptor, i. e., an organic base, for example, a slowly dropped to -15 C. at which point it was tertiary amine such as pyridine, dimethylaniline 20 maintained for 10 minutes. The white solid and the like. It is desirable to use an excess, diioctafiuoropentanoyl)peroxide, e. g., 10-50%, of the halogenating agent. 0

Typical preparations of the intermediate poly- I Ii fluoroalkanoyl chlorides and bromides are described below; which separated from the aqueous solution, was

A mixture of 11 parts of octafiuoropentanoic taken up in 10 Parts Of pelfluoromethylsycloacid, mcF-mcoon, 8.2 parts of thionyl chlchexane and separat d f the aqu us l y r, ride, a d 0,15 part of pyridine was refluxed for which was then extracted with an additional 10 one hour. Distillation of the reaction mixture Darts of'cold C.) perfluoromethylcyclogave a fraction, 9 parts of octaflugrgpentanoyl 3o hexane. The extract was combined with the main chloride, H(CF2)4COC1, boiling at 81-89" C. On ution of peroxide and stored at low temp redistillation of this material 8 parts of pure octa- Wm A sample f this P o solufluoropentanoyl chloride boiling at 84.5-86.5 C. film when med to room temperature bubbled was bt d vigorously. The white solid peroxide was ob- Twenty (20 parts of octafluoropentanoyl b tained by cooling the perfluoromethylcyclohexane mide, H(CF2)4COB1, boiling at 97-101 C, a solution to 25 C. and filtering while at this temprepared by refluxing 23 parts of octafluoro enperature. It is advisable to store the product, tanoic acid with 20.6 parts of phosphorus {34- either as a solid or in a suitable solvent, at low bromide, the temperature of reflux being 140 C. temperature. e w 0 C.

agatgliembeginning and 120 C. at the end of the Example H Polyfluoroalkanoic acids from which the inter- To Part of Sodium Peroxide and Parts 0! mediate acid halides are derived, can be obtained we was added a cold solutwn of by oxidation of the corresponding 1 fi part of hexadecafiuorononanoylchloride, alkanols in accordance to the method described 45 mm om in U. S. application Serial No. 65,065, filed in the name of Berry on December 13, 1948. For (B. P. 166.5" C.), in 10 parts of perfluoromethylexample, a polyfluoroalkanol is dissolved in a cyclohexane. The reaction was continued with suitable solvent, i. e., a saturated carboxylic acid agltation while the temperature was allowed to such as acetic acid or water solutions thereof, 60 rise slowly to 250 At this q the perfluom and treated portionwise at preferably to methylcyclohexane layer containing the di hexa- C. with an alkali or alkaline earth permanganate decafiuomnonanoyl) 'pemxlde' such as, for example, potassium permanganate. 0 0 The lliesllltiltlfi polyfluoroalkanoic acid is isolated rl cr, s o-o cri)ln fig: i g fi m g gg j gg gig the was separated from the aqueous layer and stored Polyfluoroalkanols are described in U. s. appliat E I m cation Serial No. 65,063, filed in the name of R. M. Joyce on December 13, 1948. These fluo- T0 8 stirred solution 01 0 p r 0! sodiu rinated alcohols are prepared by heating at a Chloride in 40 Parts Of Water cooled to C- W temperature of 50-350 C. a mixture of tetraslowly added P Of sodium p o This fluoroethylene and methanol in the presence of solution was then cooled to a 3 Parts a free-radical producing catalyst. The resulting 0f p fl ylry c l r de. F CF2 aC0Cl mixture can be separated into definite fractions 3941 Was added drOpWise with stirby appropriate methods such as steam distilia- 06 ring Over fi te te urin this tion, fractional distillation, fractional crystallizaaddition the temperature rose to stirring tions and the like, or may be oxidized as such to was stopped and 46 Pa f ne was addeda mixture or the corresponding polyfluoroalkanoic The r t n w -p as ystem was stirred f r acids. ten minutes while maintaining the temperature Polyfiuoroalkanoic acids from which the inter- The cold buts-I19 layer was t mediate polyfluoroalkanoyl halides may be preseparated and Stored at This butane d, can 1 be produced by electrolysis f solution on analysis showed a peroxide content alkanoic acids in substantially anhydrous hydroor Parts of duheptafluorobutyryl) peroxidegen fluoride and subsequently hydrolyzing the 0 0 resulting fluorinated acid fluoride. A whole series F P;

Other di(polyfluoroalkanoyl) peroxides of the invention can be prepared by following the foregoing procedures and substituting in the proper chemical proportions other fluorinated acid halides for those specified above. For example, by substituting tetracosafluorotridecanoyl chloride (0.84 part) for hexadecafluoronanoyl chloride (0.78 part) in Example II di(tetracosafluorotridecanoyl) peroxide,

It will be understood that the foregoing exan. v ples merely illustrate typical preparations of the fiuorinated acyl peroxides of this invention and that the invention is not restricted to these peroxides made in any particular manner.

Examples of the fluorinated acyl peroxides of this invention are:

and the like. Because of the more ready availability of the preparative raw materials those peroxides which, exclusive of the group,

have from 4 to 24 carbon atoms, are preferred, i. e., the peroxides of the straight chain polyfluoroalkanoic acids which, exclusive of the carboxyl carbon atom, have from 2 to 12 carbon atoms, exclusive.

The peroxides of this invention are excellent polymerization catalysts. They have the advantage over other known diacyl peroxides commonly employed for this purpose, of initiating polymerization at lower temperatures. In many instances, better quality and also higher molecular weight polymers can be obtained by the use of these new fluorinated acyl peroxides. Moreover, the new peroxides are useful for the polymerization of a wide variety of polymerizable unsaturated compounds, broadly the polymerizable ethylenically unsaturated monomeric organic compounds having a group, and particularly the vinylidene, including vinyl, compounds and the polyfluoroethylenes. For example, acrylonitrile parts) when heated at 30 C. with 0.5 part of a 20% perfluoromethylcyclohexane solution of di(octafluoropentanoyl) peroxide catalyst, polymerizes completely in onehalf hour. Di(hexadecafluorononanoyl) peroxide (1 part of the perfluoromethylcyclohexane solution of the peroxide described in Example 11) when added to 10 parts of acrylonitrile, gives similar results in 15 minutes at 50 C. Even at a temperature as low as 0 C., substantial polymerization of both acrylonitrile and methyl methacrylate is achieved after 15 hours with this new peroxide catalyst.

Other vinylidene and vinyl compounds which can be polymerized and copolymerized with' the di(polyfiuoroalkanoyl)peroxides of the invention include broadly the acrylyl and alkacrylyl compounds, e. g., the acrylates and methacrylates, methacrylic acid, acrylamides, methacrylamides, etc.; vinyl and vinylidene halides, e. g., vinyl chloride, vinyl fluoride, vinyl bromide, vinylidene chloride, vinylidene fluoride; vinyl carboxylates, e. g., vinyl acetate and vinyl stearate; vinyl ketones, e. g., methyl vinyl ketone; vinyl ethers, e. g., vinyl methyl ether; vinyl imides, e. g., N-vinylmaleimide; N-vinyllactams, e. g., N-vinyl-. caprolactam; and other vinyl derivatives such as vinylpyridine.

Polymerization of olefins is likewise achieved at low temperatures as is outlined below:

To a stainless steel bomb of 1600 ml. capacity, cooled in a Dry Ice-acetone bath was added parts of perfluoromethylcyclohexane and 20 parts of a 12% perfluoromethylcyclohexane solution of di(octafiuoropentanoyl) peroxide,

The bomb was closed, kept cold in a Dry Iceacetone bath, evacuated, and charged with 201 parts of ethylene. The bomb was then warmed to 0 C. and maintained at this temperature for 20 hours with agitation. The pressure during this time was 750-800 lb./sq. in. After the excess ethylene had been bled oil, the reaction mixture was filtered to remove the polymer which was in 18 parts of butane was employed as the catalyst to polymerize ethylene at 39-42 C. under an ethylene pressure of 960-1000 atm. in a stainless steel shaker tube of 1000 ml. capacity. After 25 hours reaction a total of 155 atm. of ethylene had been absorbed and 23 parts of white solid ethylene polymer, washed with acetone and dried at 108 C., was obtained. A filmpressed from this polymer at C.was orientable and extremely tough. The density of this film was 0.945 g./ml. at 25 C.

Likewise, ethylene can be copolymerized with a variety of comonomers including vinyl acetate and carbon monoxide using the peroxides of this invention.

Additional unsaturated hydrocarbons which can be similarly polymerized include the diolefins, e. g., butadiene and isoprene; and the vinylic hydrocarbons, e. g., styrene and vinyl acetylene.

The new peroxides are especially useful for low temperature polymerizations oi' the polyfluoroethylenes such as chlorotrifluoroethylene, tetrafluoroethylene, 1,1-difluoro-2,2-dichloroethylene and 1,2-difluoro-1,2-dichloroethylene. Application to this type of monomer is illustrated below with chlorotriilucroethylene.

To a 300-cc. silver-lined pressure vessel cooled in a Dry Ice-acetone bath, there was added 10 parts of a 12% perfluoromethylcyclohexane solution of di(oct-afluoropentanoyl) peroxide. The reactor, still immersed in the Dry Ice-acetone bath, was then closed, evacuated, and charged with 50 parts of purified chlorotrifluoroethylene after which it was warmed to 25-30 C. and the reaction continued at this temperature for 8 hours with vigorous agitation. From this run 38 parts of white chlorotrifluoroethylene polymer was obtained.

In addition the new peroxides effect copolymerization of derivatives, e. g., the monoand di-esters, of maleic acid and fumaric acid with vinyl and vinylidene monomers.

The di(polyfluoroalkanoyl)peroxides of this invention are also useful as free radical crosslinking agents, particularly in the vulcanization of rubber, and as catalysts for halogenation, i. e., chlorination and bromination, reactions, chlorosulfonatlon, and in other free radical reactions.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as delined in the appended claims.

The invention claimed is:

1. A fluorinated acyl peroxide having the formula:

0 o B(CFz). -00( 3(CF=).B wherein Bis from the group consisting of hydrogen and fluorine, and n is an integer of at least two.

2. A fluorinated acyl peroxide as set forth in claim 1 wherein n is an integer from 2 to 24, inclusive.

3. A fiuorinatedacyl peroxide as set forth in claim 1 wherein n is an integer from 2 to 12, inclusive.

4. A fluorinated acyl peroxide having the formula:

0 f H(C F;).. J0-0-('J(CF|)H wherein n is an integer from 2 to 24, inclusive.

5. A fluorinated acylperoxide having the formula:

o 0 v r crmtLo-oli-(c ro-r wherein n is an integer from 2 to 24, inclusive.

6. Process of preparing a fluorinated acyl peroxide which comprises reacting a polyfluoroalkanoyl halide having the formula:

0 B c FahE-X wherein B is from the group consisting of hydrogen and fluorine, n is an integer of at least 2, and X is from the group consisting of bromine and chlorine, with an inorganic peroxide.

'7. Process as set forth in claim 6 wherein said inorganic peroxide is from the group consisting of the alkali and alkaline earth metal peroxides.

8. Process of preparing a fluorinated acyl peroxide which comprises gradually adding a polyfluoroalkanoyl halide having the formula:

0 awnin -x wherein B is from the group consisting of hydrogen and fluorine, n is an integer of at least 2, and X is from the group consisting of bromine and chlorine, to an aqueous solution of sodium peroxide, said aqueous solution being maintained at a temperature of 40 C. to +5 C. and the amount of polyfluoroalkanoyl halide added being limited to not in excess of 2 moles to each mole of sodium peroxide in said aqueous solution.

ORVILLE H. BULLITT, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,614,037 McKee Jan. 11, 1927 1,913,775 Straub June 13, 1933 2,501,967 Vaughan et al Mar. 28, 1950 OTHER REFERENCES Panizzon: Helv. Chim. Acta. vol. 15, pages 1187 to 1194 (1932).

Certificate of Correction Patent No. 2,559,630 July 10, 1951 ORVILLE H. BULLITT, JR.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 5, line 43, for that portion of the formula reading (CF F and that the said Letters Patent should be read as corrected above, so that the same may cofiform to the record of the case in the Patent Ofiice.

Signed and sealed this 25th day of September, A. D. 1951.

[smr] THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

1. A FLUORINATED ACYL PEROXIDE HAVING THE FORMULA: 